Modelling of radiological risks in farms around mines, Rustenburg, South Africa
摘要
Mining, industrial and agricultural activities have been widely reported to enhance environmental radioactivity levels globally. To ensure human exposure to environmental radioactivity is as low as reasonably achievable (ALARA), radiological measurement and modelling of radionuclides in the environment and their various exposure pathways are essential. In this study, a Broad energy germanium detector was used to measure the concentration of 238U, 232Th and 40K in soil collected from Rustenburg, one of the mining cities in South Africa. Radiological hazard for a hypothetical resident farmer was simulated for three sites: site A (outside farming area), B (organic farm area) and C (inorganic farm area), using the Residual Radioactivity (RESRAD) computer code. Measured activity concentration of 40K, 232Th and 238U in all study sites was found to be less than global average values of 400 Bq/kg, 35 Bq/kg and 30 Bq/kg reported by the United Nations Scientific Committee on the Effects of Atomic Radiation, respectively. The maximum total effective dose and excess life cancer risk estimated using the RESRAD-offsite code in site A are 0.5190 mSv/yr and 8.58, at year 16.92 and year 0, respectively. Total excess life cancer risk is observed to be above 2.90 × 10−4, though the total effective dose is lower than 1 mSv/yr reported by UNSCEAR (2000). Similarly, the total effective dose and excess life cancer risk, estimated using RESRAD-onsite Code in sites B and C, are below the global average of 1 mSv/yr and 2.90 × 10−4, respectively. Therefore, the study reveals that agricultural practices contribute less to radiological hazards in the study area than mining activities. Regular environmental measurement and monitoring are recommended to ensure resident exposure is as low as reasonably achievable.